In a method for adapting an injection valve characteristic of an activated fuel injection valve of an internal combustion engine to age-related changes of its actual injection behavior (DE 102 57 686 A1), the injection valve is intermittently activated during an operating state of the internal combustion engine which does not require any fuel injection, while otherwise no fuel injection occurs. At least one working cycle with activation follows or precedes a working cycle without activation of the injection valve. One speed value of the internal combustion engine is detected in each case for the working cycle with activation and for at least one of the working cycles without activation, a difference of the detected values is calculated, and a correction of the injection characteristic is thus performed.
Dosing the injected fuel quantity precisely is of decisive significance for the exact control of internal combustion engines. The injected quantity is a function of the parameters opening duration and needle stroke in modern piezo injection valves having direct drive. In the above-mentioned method, only the opening duration of the injection valve is adapted to age-related changes of the injection behavior.